From patchwork Mon Nov 14 22:48:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13042931 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EE0CCC433FE for ; Mon, 14 Nov 2022 23:34:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ouie4-0002Lh-Tq; Mon, 14 Nov 2022 18:13:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ouids-0001eb-SA for qemu-devel@nongnu.org; Mon, 14 Nov 2022 18:13:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ouiGC-0002Lv-BW for qemu-devel@nongnu.org; Mon, 14 Nov 2022 17:49:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668466139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kzTEBYqs7XYX4CjhiYRYgBnv2AzlV5X742T2Py1Whn8=; b=DiLJIHkJ17SkiiDpKQAyedNJApetQB/rkfXCxxT1/jFEKv41vmQXMcEiCCoPRmkX4wBYPo kiueSPyT1PBjUlzbEkromRc579zuvzIFfIUvUWrQsuLYNWtSZ1TPgJmyfQJy3W8PHeIF6F 34e8f6n3yfIr+/qLH0wVAlqXJxvNdRs= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-584-2mtY7N2BO5aHhvGgVXZN8g-1; Mon, 14 Nov 2022 17:48:55 -0500 X-MC-Unique: 2mtY7N2BO5aHhvGgVXZN8g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2B2BC85A59D; Mon, 14 Nov 2022 22:48:55 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8B91940B48EA; Mon, 14 Nov 2022 22:48:54 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, libguestfs@redhat.com, nbd@other.debian.org, Vladimir Sementsov-Ogievskiy Subject: [PATCH v2 01/15] nbd/client: Add safety check on chunk payload length Date: Mon, 14 Nov 2022 16:48:34 -0600 Message-Id: <20221114224848.2186298-2-eblake@redhat.com> In-Reply-To: <20221114224848.2186298-1-eblake@redhat.com> References: <20221114224141.cm5jgyxfmvie5xb5@redhat.com> <20221114224848.2186298-1-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Our existing use of structured replies either reads into a qiov capped at 32M (NBD_CMD_READ) or caps allocation to 1000 bytes (see NBD_MAX_MALLOC_PAYLOAD in block/nbd.c). But the existing length checks are rather late; if we encounter a buggy (or malicious) server that sends a super-large payload length, we should drop the connection right then rather than assuming the layer on top will be careful. This becomes more important when we permit 64-bit lengths which are even more likely to have the potential for attempted denial of service abuse. Signed-off-by: Eric Blake --- nbd/client.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/nbd/client.c b/nbd/client.c index 90a6b7b38b..cd97a2aa09 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -1412,6 +1412,18 @@ static int nbd_receive_structured_reply_chunk(QIOChannel *ioc, chunk->handle = be64_to_cpu(chunk->handle); chunk->length = be32_to_cpu(chunk->length); + /* + * Because we use BLOCK_STATUS with REQ_ONE, and cap READ requests + * at 32M, no valid server should send us payload larger than + * this. Even if we stopped using REQ_ONE, sane servers will cap + * the number of extents they return for block status. + */ + if (chunk->length > NBD_MAX_BUFFER_SIZE + sizeof(NBDStructuredReadData)) { + error_setg(errp, "server chunk %" PRIu32 " (%s) payload is too long", + chunk->type, nbd_rep_lookup(chunk->type)); + return -EINVAL; + } + return 0; }